As conventional tilt angle detecting apparatus for vehicle including an angular velocity sensor mounted in a vehicle, for detecting the tilt angle of the vehicle, there are, for example, the following conventional examples. As conventional example 1, there has been provided a tilt angle detecting apparatus for vehicle which is aimed at correctly correcting the offset error of an angular velocity sensor (a yaw rate sensor) for detecting the rotation angle velocity of the vehicle, which, as the correcting method, uses an offset correction method of correcting the offset of a gyro sensor in performing a tracking operation for satellite reception, and, when the offset error is large, increases the frequency with which the tilt angle detecting apparatus for vehicle corrects the offset error and then, when this correction of the offset error advances and the offset error becomes small, reduces the frequency with which it makes an incorrect correction (for example, refer to patent reference 1).
As conventional example 2, there has been provided a tilt angle detecting apparatus for vehicle which is aimed at making it possible to make an offset correction to an angular velocity sensor, and to diagnose the sensitivity of the angular velocity sensor, which, by using an offset correction unit, acquires an offset correction value from an angular velocity value which is acquired from detection signals which are outputted by a plurality of angular velocity sensors, and a detection signal which is outputted by an angular velocity sensor mounted in a vehicle which is standing still, and then makes an offset correction to the angular velocity value using the offset correction value, and which, by using a sensor sensitivity diagnostic unit, detects that the vehicle is making a turn on the basis of the detection signals of the plurality of angular velocity sensors, and then diagnoses the sensitivities of a plurality of angle sensors from the angular velocity values of the plurality of angular velocity sensors which have been offset-corrected while the vehicle is making a turn (for example, refer to patent reference 2).    [Patent reference 1] Japanese patent No. 3413327    [Patent reference 2] JP, 2005-172662, A
The conventional tilt angle detecting apparatuses for vehicle are constructed as mentioned above, and conventional example 1 (patent reference 1) and conventional example 2 (patent reference 2) achieve their objectives, respectively.
A problem is, however, that when any of these conventional exemplary methods is applied to an angular velocity sensor for detecting the angular velocity of a vehicle in a roll direction of the vehicle, peripheral equipment has to be additionally disposed and a more complicated system configuration is needed.
The present invention is made in order to solve the above-mentioned problem, and it is therefore an object of the present invention to provide a tilt angle detecting apparatus for vehicle which makes it possible to detect a tilt angle of a vehicle in a roll direction of the vehicle correctly without having to additionally include peripheral equipment and with a simple structure, and a rollover judging apparatus which uses the tilt angle detecting apparatus for vehicle.